Speaker grill mounting plate



FIG. 1 is a perspective view of a speaker grill mounting plate showing my new design;

FIG. 2 is a top plan view; and,

FIG. 3 is a side elevation view.

The broken line showing in FIGS. 1 and 2 is for illustrative purposes only and forms no part of the claimed design. The surfaces or portions of the article not shown in the drawing or described in the specification form no part of the claimed design. 

The ornamental design for a speaker grill mounting plate, as shown and described. 